How to Monitor Network Uptime

I just bought a server at a new hosting provider, and I want to make sure the network stays up. What is the best way to monitor my network? I just tried out icpld and it already reported some downtime, but I have no way of telling how reliable icpld is.

If you have a bunch of servers in your server farm, use a minimum of two external alert/monitoring services, with testing period of say 5 minutes (i.e. services are tested every 5 minutes), for more ciritical systems you can go to 2 minutes. Some providers (including us), have leased servers worldwide and intalled softwares on them to monitor our network. A good software that I know of is GFi Server Monitor.